Systems and methods for optimizing a compliance voltage of an auditory prosthesis

ABSTRACT

Exemplary systems and methods for optimizing a compliance voltage of an auditory prosthesis are disclosed. Each stimulation channel formed by electrodes that are coupled to an auditory prosthesis may have an adjustable current steering range associated therewith. Each adjustable current steering range is centered about the midpoint of its respective stimulation channel and defines a range of current steering that may be used within its respective stimulation channel. A compliance voltage of an auditory prosthesis may be optimized by setting a current steering range for one or more stimulation channels to a value that results in an optimum balance between power conservation and performance of the auditory prosthesis.

BACKGROUND INFORMATION

The sense of hearing in human beings involves the use of hair cells inthe cochlea that convert or transduce audio signals into auditory nerveimpulses. Hearing loss, which may be due to many different causes, isgenerally of two types: conductive and sensorineural. Conductive hearingloss occurs when the normal mechanical pathways for sound to reach thehair cells in the cochlea are impeded. These sound pathways may beimpeded, for example, by damage to the auditory ossicles. Conductivehearing loss may often be helped by the use of conventional hearing aidsthat amplify sound so that audio signals reach the cochlea and the haircells. Some types of conductive hearing loss may also be treated bysurgical procedures.

Sensorineural hearing loss, on the other hand, is caused by the absenceor destruction of the hair cells in the cochlea which are needed totransduce acoustic signals into auditory nerve impulses. People whosuffer from sensorineural hearing loss may be unable to derivesignificant benefit from conventional hearing aid systems, no matter howloud the acoustic stimulus is. This is because the mechanism fortransducing sound energy into auditory nerve impulses has been damaged.Thus, in the absence of properly functioning hair cells, auditory nerveimpulses cannot be generated directly from sounds.

To overcome sensorineural hearing loss, numerous auditory prosthesissystems (e.g., cochlear implant systems) have been developed. Auditoryprosthesis systems bypass the hair cells in the cochlea by presentingelectrical stimulation directly to stimulation sites (e.g., auditorynerve fibers) by way of one or more channels formed by an array ofelectrodes implanted in an auditory prosthesis patient. Directstimulation of the stimulation sites leads to the perception of sound inthe brain and at least partial restoration of hearing function.

Some conventional auditory prosthesis systems may be configured to usecurrent steering to apply electrical stimulation to stimulation sitesnot directly associated with the electrodes implanted within an auditoryprosthesis patient. For example, an auditory prosthesis system mayconcurrently stimulate multiple (e.g., two) electrodes that surround,but that are not directly associated with, a particular stimulation sitein order to steer current to (and thereby apply electrical stimulationto) the stimulation site. One advantage of current steering is that thecurrent used to concurrently stimulate the multiple electrodes is splitbetween the multiple electrodes, thereby reducing the compliance voltage(i.e., the voltage maintained by the auditory prosthesis that governs amaximum level of stimulation current that can be delivered by theauditory prosthesis) required to generate the current. Unfortunately,however, even when current steering is used in a conventional auditoryprosthesis system, the auditory prosthesis has to maintain a relativelyhigh compliance voltage to account for situations in which the desiredstimulation site is directly associated with a single electrode. In suchsituations, a relatively high compliance voltage is required because allof the current is applied to the single electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various embodiments and are a partof the specification. The illustrated embodiments are merely examplesand do not limit the scope of the disclosure. Throughout the drawings,identical or similar reference numbers designate identical or similarelements.

FIG. 1 illustrates an exemplary auditory prosthesis system according toprinciples described herein.

FIG. 2 shows a plurality of electrodes that define a plurality ofstimulation channels according to principles described herein.

FIG. 3 illustrates exemplary components of a sound processor accordingto principles described herein.

FIG. 4 shows a particular stimulation channel defined by first andsecond physical electrodes according to principles described herein.

FIG. 5 illustrates exemplary components of an auditory prosthesisaccording to principles described herein.

FIG. 6 illustrates an exemplary method of optimizing a compliancevoltage of an auditory prosthesis according to principles describedherein.

FIG. 7 illustrates another exemplary method of optimizing a compliancevoltage of an auditory prosthesis according to principles describedherein.

FIG. 8 shows an exemplary mapping strategy according to principlesdescribed herein.

DETAILED DESCRIPTION

Systems and methods for optimizing a compliance voltage of an auditoryprosthesis (e.g., an implantable cochlear stimulator) are describedherein. As will be described below, each stimulation channel formed byelectrodes that are coupled to an auditory prosthesis may have anadjustable current steering range associated therewith. Each adjustablecurrent steering range is centered about the midpoint of its respectivestimulation channel and defines a range of current steering that may beused within its respective stimulation channel. A compliance voltage ofan auditory prosthesis may be optimized by setting a current steeringrange for one or more stimulation channels to a value that results in anoptimum balance between power conservation and performance of theauditory prosthesis.

To illustrate, the current steering range associated with one or morestimulation channels may be decreased in order to decrease thecompliance voltage required by an auditory prosthesis and therebydecrease the amount of power consumed by the auditory prosthesis.However, because the range of current steering that may be used by theauditory prosthesis is also reduced as the current steering range isdecreased, an overall performance level of the auditory prosthesis mayalso be decreased as the current steering range is decreased. Hence, insome examples (e.g., when power conservation is relatively lessimportant than performance), the compliance voltage may be optimized byincreasing the current steering range associated with one or morestimulation channels in order to increase a performance level of theauditory prosthesis.

FIG. 1 illustrates an exemplary auditory prosthesis system 100. Auditoryprosthesis system 100 may include a microphone 102, a sound processor104, a headpiece 106 having a coil 108 disposed therein, an auditoryprosthesis 110, and a lead 112 with a plurality of electrodes 114disposed thereon. Additional or alternative components may be includedwithin auditory prosthesis system 100 as may serve a particularimplementation.

As shown in FIG. 1, microphone 102, sound processor 104, and headpiece106 may be located external to an auditory prosthesis patient. In somealternative examples, microphone 102 and/or sound processor 104 may beimplanted within the patient. In such configurations, the need forheadpiece 106 may be obviated.

Microphone 102 may detect an audio signal and convert the detectedsignal to a corresponding electrical signal. The electrical signal maybe sent from microphone 102 to sound processor 104 via a communicationlink 116, which may include a telemetry link, a wire, and/or any othersuitable communication link.

Sound processor 104 is configured to direct auditory prosthesis 110 togenerate and apply electrical stimulation (also referred to herein as“stimulation current”) to one or more stimulation sites associated withan auditory pathway (e.g., the auditory nerve) of the patient. Exemplarystimulation sites include, but are not limited to, one or more locationswithin the cochlea, the cochlear nucleus, the inferior colliculus,and/or any other nuclei in the auditory pathway. To this end, soundprocessor 104 may process the audio signal detected by microphone 102 inaccordance with a selected sound processing strategy to generateappropriate stimulation parameters for controlling auditory prosthesis110. Sound processor 104 may include or be implemented by abehind-the-ear (“BTE”) unit, a body-worn portable speech processor(“PSP”), and/or any other sound processing unit as may serve aparticular implementation. Exemplary components of sound processor 104will be described in more detail below.

Sound processor 104 may be configured to transcutaneously transmit oneor more control parameters and/or one or more power signals to auditoryprosthesis 110 with coil 108 by way of a communication link 118. Thesecontrol parameters may be configured to specify one or more stimulationparameters, operating parameters, and/or any other parameter by whichauditory prosthesis 110 is to operate as may serve a particularimplementation. Exemplary control parameters include, but are notlimited to, stimulation current levels, volume control parameters,program selection parameters, operational state parameters (e.g.,parameters that turn a sound processor and/or an auditory prosthesis onor off), audio input source selection parameters, fitting parameters,noise reduction parameters, microphone sensitivity parameters,microphone direction parameters, pitch parameters, timbre parameters,sound quality parameters, most comfortable current levels (“M levels”),threshold current levels, channel acoustic gain parameters, front andbackend dynamic range parameters, current steering parameters, pulserate values, pulse width values, frequency parameters, amplitudeparameters, waveform parameters, electrode polarity parameters (i.e.,anode-cathode assignment), location parameters (i.e., which electrodepair or electrode group receives the stimulation current), stimulationtype parameters (i.e., monopolar, bipolar, or tripolar stimulation),burst pattern parameters (e.g., burst on time and burst off time), dutycycle parameters, spectral tilt parameters, filter parameters, anddynamic compression parameters. Sound processor 104 may also beconfigured to operate in accordance with one or more of the controlparameters. Additional features of sound processor 104 will be describedin more detail below.

As shown in FIG. 1, coil 108 may be housed within headpiece 106, whichmay be affixed to a patient's head and positioned such that coil 108 iscommunicatively coupled to a corresponding coil included within auditoryprosthesis 110. In this manner, control parameters and power signals maybe wirelessly transmitted between sound processor 104 and auditoryprosthesis 110 via communication link 118. It will be understood thatdata communication link 118 may include a bi-directional communicationlink and/or one or more dedicated uni-directional communication links.In some alternative embodiments, sound processor 104 and auditoryprosthesis 110 may be directly connected with one or more wires or thelike.

Auditory prosthesis 110 may include any type of implantable stimulatorthat may be used in association with the systems and methods describedherein. For example, auditory prosthesis 110 may include an implantablecochlear stimulator. In some alternative implementations, auditoryprosthesis 110 may include a brainstem implant and/or any other type ofauditory prosthesis that may be implanted within a patient andconfigured to apply stimulation to one or more stimulation sites locatedalong an auditory pathway of a patient.

In some examples, auditory prosthesis 110 may be configured to generateelectrical stimulation representative of an audio signal detected bymicrophone 102 in accordance with one or more stimulation parameterstransmitted thereto by sound processor 104. Auditory prosthesis 110 maybe further configured to apply the electrical stimulation to one or morestimulation sites within the patient via one or more stimulationchannels formed by electrodes 114 disposed along lead 112.

To illustrate, FIG. 2 shows a plurality of electrodes E1-E4 (alsoreferred to herein as “physical electrodes”) that define a plurality ofstimulation channels 202-1 through 202-3 (collectively “stimulationchannels 202”). Physical electrodes E1 and E2 define a first stimulationchannel 202-1, physical electrodes E2 and E3 define a second stimulationchannel 202-2, and physical electrodes E3 and E4 define a thirdstimulation channel 202-3. Each stimulation channel 202 may have aparticular frequency band 204 (e.g., frequency bands 204-1 through204-3) associated therewith. For example, frequency band 204-1 comprisesfrequencies f₁ through f₂ and is associated with stimulation channel202-1, frequency band 204-2 comprises frequencies f₂ through f₃ and isassociated with stimulation channel 202-2, and frequency band 204-3comprises frequencies f₃ through f₄ and is associated with stimulationchannel 202-3. As will be described below, a frequency associated with(e.g., included within) an audio signal and included within a particularfrequency band (e.g., frequency band 204-1) may be represented bystimulating one or more of the physical electrodes (e.g., physicalelectrodes E1 and/or E2) that define the stimulation channel (e.g.,stimulation channel 202-1) associated with the particular frequencyband.

FIG. 3 illustrates exemplary components of sound processor 104. As shownin FIG. 3, sound processor 104 may include a communication facility 302,a current steering management facility 304, a mapping facility 306, aspectral analysis facility 308, and a storage facility 310, which may bein communication with one another using any suitable communicationtechnologies. Each of these facilities 302-310 may include anycombination of hardware, software, and/or firmware as may serve aparticular implementation. For example, one or more of facilities302-310 may include a computing device or processor configured toperform one or more of the functions described herein. Facilities302-310 will now be described in more detail.

Communication facility 302 may be configured to facilitate communicationbetween sound processor 104 and auditory prosthesis 110. For example,communication facility 302 may include transceiver components configuredto wirelessly transmit data (e.g., control parameters and/or powersignals) to auditory prosthesis 110 and/or wirelessly receive data fromauditory prosthesis 110.

Current steering management facility 304 may be configured to performone or more current steering management operations. For example, currentsteering management facility 304 may be configured to determine, set,adjust, or otherwise modify a current steering range for a stimulationchannel defined by first and second physical electrodes communicativelycoupled to an auditory prosthesis.

As mentioned, a current steering range associated with a stimulationchannel may be centered about the midpoint (which may be the arithmeticmean or the geometric mean) of the stimulation channel and defines arange of current steering that may be used within the stimulationchannel. To illustrate, FIG. 4 shows a particular stimulation channel402 defined by first and second physical electrodes E1 and E2.Stimulation channel 402 may be associated with any frequency band as mayserve a particular implementation. In the example of FIG. 4, stimulationchannel 402 is associated with a frequency band having a minimumfrequency of 300 Hz and a maximum frequency of 400 Hz. It will berecognized that the current steering range may alternatively be centeredabout any other point within the stimulation channel as may serve aparticular implementation.

As shown, stimulation channel 402 may be conceptualized as having aplurality of virtual electrodes 404 (e.g., virtual electrodes 404-1,404-2, and 402-3) disposed in between physical electrodes E1 and E2.Each virtual electrode 404 represents a particular location along anelectrode lead (e.g., lead 112) and in between physical electrodes E1and E2. For example, virtual electrode 404-2 represents a midpoint ofstimulation channel 402 about which a current steering range associatedwith stimulation channel 402 is centered.

The current steering range associated with stimulation channel 402 mayinclude any number of the virtual electrodes 404 included in stimulationchannel 402, and, in some instances, may also include physicalelectrodes E1 and E2. In some examples, the current steering rangeassociated with stimulation channel 402 may be set by setting acorresponding current steering range value to any value in between andincluding zero and one. For example, a current steering range value maybe set to zero to minimize the current steering range about the midpointof stimulation channel 402 (i.e., only include virtual electrode 404-2)and thereby direct the auditory prosthesis to not use current steeringabout the midpoint of stimulation channel 402. In other words, anyfrequency included in the frequency band associated with stimulationchannel 402 (i.e., any frequency in between and including 300 Hz and 400Hz) is represented by concurrently stimulating the first and secondphysical electrodes E1 and E2 with a substantially equal amount ofcurrent.

Alternatively, the current steering range value associated withstimulation channel 402 may be set to one to maximize the currentsteering range about the midpoint of stimulation channel 402 (i.e., setthe current steering range to be substantially equal to an entirephysical range of stimulation channel 402, which includes both physicalelectrodes E1 and E2 as well as all of the virtual electrodes 404disposed therebetween) and thereby direct the auditory prosthesis to usefull current steering about the midpoint of stimulation channel 402. Inother words, each frequency in between (but not including) a minimumfrequency (i.e., 300 Hz) and a maximum frequency (i.e., 400 Hz) includedin a frequency band associated with the stimulation channel isrepresented by concurrently stimulating the first and second physicalelectrodes E1 and E2 with a unique ratio of current. However, theminimum frequency (i.e., 300 Hz) is represented by applying all of thecurrent to the first physical electrode E1 and the maximum frequency(i.e., 400 Hz) is represented by applying all of the current to thesecond physical electrode E2.

The current steering range value associated with stimulation channel 402may be set to any other value in between zero and one in order to setthe current steering range to any other range within the physical rangeof stimulation channel 404.

In some examples, current steering management facility 304 may set acurrent steering range for a particular stimulation channel to be lessthan an entire physical range of the stimulation channel. In thismanner, as will be described below, current steering management facility304 may ensure that current is always split between the two physicalelectrodes that define the stimulation channel, thereby reducing thecompliance voltage needed to generate the current. As will be describedbelow, a reduced compliance voltage may result in the auditoryprosthesis consuming a reduced amount of power.

In some examples, current steering management facility 304 may set asingle current steering range and apply the single current steeringrange to a plurality of stimulation channels (e.g., all of thestimulation channels associated with auditory prosthesis 110).Alternatively, current steering management facility 304 may set a uniquecurrent steering range for each stimulation channel associated withauditory prosthesis 110.

In some examples, current steering range management facility 304 may seta current steering range in response to input provided to soundprocessor 104 by a user. Additionally or alternatively, as will bedescribed below, current steering range management facility 304 mayautomatically set a current steering range in response to one or morefactors. For example, as will be described in more detail below, currentsteering range management facility 304 may determine a relativeimportance of performance versus power conservation for auditoryprosthesis 110 and set the current steering range in accordance with thedetermined relative importance. As another example, current steeringrange management facility 304 may detect a change (e.g., a decrease) inpower available to auditory prosthesis 110 and adjust (e.g., decrease)the current steering range in response to the change in available power.Additional current steering management operations that may be performedby current steering management facility 304 will be described below.

Returning to FIG. 3, mapping facility 306 may be configured to map thefrequencies included a frequency band associated with a stimulationchannel to one or more electrodes (physical and/or virtual) included inthe current steering range of the stimulation channel. To illustrate,with reference again to FIG. 4, each frequency in between and including300 Hz and 400 Hz may be mapped to physical electrodes E1 and E2 and/orany number of virtual electrodes 404 in accordance with a currentsteering range set by current steering range management facility 304 forstimulation channel 402.

For example, line 406-1 represents an exemplary frequency-to-electrodemapping when the current steering range value (referred to as “σ” inFIG. 4) has been set to zero. In this case, the current steering rangeis limited to include only the virtual electrode (i.e., virtualelectrode 404-2) located at the midpoint of stimulation channel 404.Hence, as illustrated by line 406-1, each frequency in between andincluding 300 Hz and 400 Hz is mapped to virtual electrode 404-2.

Two additional frequency-to-electrode mappings are also illustrated inFIG. 4. For example, line 406-2 represents an exemplaryfrequency-to-electrode mapping when the current steering range value hasbeen set to 0.5. In this case, the current steering range is limited tohalf of the entire physical range of stimulation channel 402 andincludes virtual electrodes 404-1 and 404-3 as well as the virtualelectrodes 404 disposed therebetween. Hence, as illustrated by line406-2, each frequency in between and including 300 Hz and 400 Hz ismapped to any of these virtual electrodes 404.

Likewise, line 406-3 represents an exemplary frequency-to-electrodemapping when the current steering range value has been set to one. Inthis case, the current steering range is substantially equal to anentire physical range of stimulation channel 402 and includes physicalelectrodes E1 and E2 as well as the virtual electrodes 404 disposedtherebetween. Hence, as illustrated by line 406-3, 300 Hz is mapped tophysical electrode E1, 400 Hz is mapped to physical electrode E2, andeach frequency in between 300 Hz and 400 Hz is mapped to virtualelectrodes 404.

Returning to FIG. 3, spectral analysis facility 308 may be configured todetect or identify one or more frequencies associated with (e.g.,included within) an audio signal presented to an auditory prosthesispatient. For example, spectral analysis facility 308 may be configuredto detect a dominant frequency included in the audio signal and includedwithin a particular stimulation channel (e.g., stimulation channel 402).

Spectral analysis facility 308 may detect one or more frequenciesassociated with an audio signal in any suitable manner as may serve aparticular implementation. For example, spectral analysis facility 308may be implemented by a plurality of band-pass filters configured todivide the audio signal into a plurality of frequency bands.Additionally or alternatively, spectral analysis facility 308 may beconfigured to convert the audio signal from a time domain into afrequency domain and then divide the resulting frequency bins into theplurality of frequency bands. To this end, spectral analysis facility308 may include one or more components configured to apply a DiscreteFourier Transform (e.g., a Fast Fourier Transform (“FFT”)) to the audiosignal.

In some examples, spectral analysis facility 308 may be configured toanalyze an acoustic spectrum of an audio signal and identify one or morespectral peaks included therein. The identified one or more spectralpeaks may be representative of one or more dominant frequencies includedin the audio signal. Spectral analysis facility 308 may utilize anyother suitable spectral analysis heuristic (e.g., one or more averagingheuristics) to identify a frequency associated with an audio signal.

In response to spectral analysis facility 308 detecting a frequencyassociated with an audio signal and included within a frequency bandassociated with a particular stimulation channel, current steeringmanagement facility 304 may identify an electrode (either physical orvirtual) to which the detected frequency is mapped. For example, withreference again to FIG. 4, spectral analysis facility 308 may detect afrequency of 300 Hz within an audio signal presented to a patient. Inresponse, current steering management facility 304 may identify anelectrode to which a frequency of 300 Hz is mapped in accordance withthe particular current steering range previously set by current steeringmanagement facility 304. For example, if the current steering rangevalue is zero, current steering management facility 304 may identifyvirtual electrode 404-2 as the electrode to which 300 Hz is mapped.Alternatively, if the current steering range value is 0.5, currentsteering management facility 304 may identify virtual electrode 404-3 asthe electrode to which 300 Hz is mapped. Alternatively, if the currentsteering range value is one, current steering management facility 304may identify physical electrode E1 as the electrode to which 300 Hz ismapped.

Current steering management facility 304 may be further configured todirect the auditory prosthesis to apply electrical stimulationrepresentative of the frequency detected by spectral analysis facility308 to a stimulation site associated with the electrode (physical orvirtual) to which the detected frequency is mapped.

To illustrate, if the mapped electrode is a virtual electrode (e.g., oneof virtual electrodes 404), current steering management facility 304 maydirect the auditory prosthesis to apply electrical stimulationrepresentative of the detected frequency by directing the auditoryprosthesis to concurrently stimulate the first physical electrode (e.g.,physical electrode E1) with a first current level and the secondphysical electrode (e.g., physical electrode E2) with a second currentlevel. The ratio of the first current level to the second current levelis based on a position of the virtual electrode within the currentsteering range of the stimulation channel. For example, with referenceto FIG. 4, if the detected frequency is 300 Hz, and the virtualelectrode to which 300 Hz is mapped is virtual electrode 404-2, an equalamount of current is applied to physical electrodes E1 and E2. However,if the virtual electrode to which 300 Hz is mapped is virtual electrode404-3, the ratio of the first current level to the second current levelis greater than one.

Alternatively, if the mapped electrode is a physical electrode (e.g.,physical electrode E1 or physical electrode E2), current steeringmanagement facility 304 may direct the auditory prosthesis to applyelectrical stimulation representative of the detected frequency bydirecting the auditory prosthesis to only stimulate the physicalelectrode. For example, with reference to FIG. 4, if the detectedfrequency is 300 Hz, and the physical electrode to which 300 Hz ismapped is physical electrode E1, all of the current is applied tophysical electrode E1.

Current steering management facility 304 may be further configured tooptimize a compliance voltage of an auditory prosthesis by setting acurrent steering range for one or more stimulation channels to a valuethat results in an optimum balance between performance and powerconservation of the auditory prosthesis. To illustrate, with referenceto FIG. 4, the compliance voltage maintained by an auditory prosthesismay be represented by I*R*(½+σ/2), where “I” represents a total amountof current applied to physical electrodes E1 and E2, “R” represents animpedance of physical electrodes E1 and E2, and “σ” represents a currentsteering range associated stimulation channel 402. Accordingly, if σ isequal to 1 (signifying full current steering about the midpoint ofstimulation channel 402), the compliance voltage is equal to I*R.Alternatively, if σ is equal to 0 (signifying no current steering aboutthe midpoint of stimulation channel 402), the compliance voltage isequal to (½)*I*R. Hence, the compliance voltage is at a maximum when σis equal to 1 and at a minimum when σ is equal to 0. However, theperformance level of the auditory prosthesis is also at a maximum when σis equal to 1 and at a minimum when σ is equal to 0. Hence, in someexamples, current steering management facility 304 may balanceperformance and power conservation by setting the current steering rangevalue σ to any suitable value (e.g., 0.5) in between 0 and 1.

Returning to FIG. 3, storage facility 310 may be configured to maintaincontrol parameter data 312 representative of one or more controlparameters, which may include one or more stimulation parameters (e.g.,current steering parameters) to be transmitted from sound processor 104to auditory prosthesis 110. Storage facility 310 may be configured tomaintain additional or alternative data as may serve a particularimplementation.

FIG. 5 illustrates exemplary components of auditory prosthesis 110. Asshown in FIG. 5, auditory prosthesis 110 may include a communicationfacility 502, a power supply facility 504, a current generation facility506, a stimulation facility 508, and a storage facility 510, which maybe in communication with one another using any suitable communicationtechnologies. Each of these facilities 502-410 may include anycombination of hardware, software, and/or firmware as may serve aparticular application. For example, one or more of facilities 502-410may include a computing device or processor configured to perform one ormore of the functions described herein. Facilities 502-410 will now bedescribed in more detail.

Communication facility 502 may be configured to facilitate communicationbetween auditory prosthesis 110 and sound processor 104. For example,communication facility 502 may include one or more coils configured toreceive control signals and/or power signals from sound processor 104.Communication facility 502 may additionally or alternatively beconfigured to transmit one or more status signals and/or other data tosound processor 104.

Power supply facility 504 may be configured to provide power to variouscomponents included within auditory prosthesis 110. To this end, powersupply facility 504 may be configured to derive a compliance voltagefrom a power signal received from sound processor 104. The compliancevoltage may be used by current generation facility 504 to generatestimulation current and/or by any other component within auditoryprosthesis 110.

Current generation facility 506 may be configured to generatestimulation current in accordance with one or more stimulationparameters received from sound processor 104. To this end, currentgeneration facility 506 may include one or more current generatorsand/or any other circuitry configured to facilitate generation ofstimulation current. For example, current generation facility 506 mayinclude an array of independent current generators each corresponding toa distinct electrode or channel. A maximum stimulation current levelthat each current generator is capable of producing is dependent in parton the compliance voltage produced by power supply facility 504.

Stimulation facility 508 may be configured to facilitate application ofthe stimulation current generated by current generation facility 506 toone or more stimulation sites within the patient in accordance with oneor more stimulation parameters received from sound processor 104. Insome examples, stimulation facility 508 may be configured to operate inaccordance with a current steering range set by sound processor 104.

Storage facility 510 may be configured to maintain data generated and/orutilized by auditory prosthesis 110. For example, storage facility 510may maintain data representative of one or more stimulation parametersconfigured to define the stimulation current generated and applied byauditory prosthesis 110.

FIG. 6 illustrates an exemplary method 600 of optimizing a compliancevoltage of an auditory prosthesis. While FIG. 6 illustrates exemplarysteps according to one embodiment, other embodiments may omit, add to,reorder, and/or modify any of the steps shown in FIG. 6. One or more ofthe steps shown in FIG. 6 may be performed by any component orcombination of components of sound processor 104.

In step 602, a sound processor sets a current steering range for astimulation channel defined by first and second physical electrodescommunicatively coupled to an auditory prosthesis to be less than anentire physical range of the stimulation channel. The current steeringrange is centered about the midpoint of the stimulation channel and maybe set to be less than the entire physical range of the stimulationchannel in any of the ways described herein. As mentioned, one benefitof limiting the current steering range in this manner is that thecompliance voltage required by the auditory prosthesis is reducedrelative to that needed when full current steering is employed.

In step 604, the sound processor maps the frequencies included in afrequency band associated with the stimulation channel to one or morevirtual electrodes included in the current steering range of thestimulation channel. Step 604 may be performed in any of the waysdescribed herein.

In step 606, the sound processor detects a frequency associated with anaudio signal and included within the frequency band. Step 606 may beperformed in any of the ways described herein.

In step 608, the sound processor identifies a virtual electrode to whichthe detected frequency is mapped. Step 608 may be performed in any ofthe ways described herein.

In step 610, the sound processor directs the auditory prosthesis toapply electrical stimulation representative of the detected frequency toa stimulation site associated with the identified virtual electrode byconcurrently stimulating the first physical electrode with a firstcurrent level and the second physical electrode with a second currentlevel. As described above, a ratio of the first current level to thesecond current level is based on a position of the identified virtualelectrode within the current steering range of the stimulation channel.Step 610 may be performed in any of the ways described herein.

FIG. 7 illustrates another exemplary method 700 of optimizing acompliance voltage of an auditory prosthesis. While FIG. 7 illustratesexemplary steps according to one embodiment, other embodiments may omit,add to, reorder, and/or modify any of the steps shown in FIG. 7. One ormore of the steps shown in FIG. 7 may be performed by any component orcombination of components of sound processor 104.

In step 702, a sound processor determines a relative importance ofperformance versus power conservation for an auditory prosthesis. Thedetermination may be performed in response to input provided by a user(e.g., a patient, clinician, etc.) specifying a particular relativeimportance. Additionally or alternatively, as will be illustrated below,the determination may be performed by the sound processor automatically.

In step 704, the sound processor determines, in accordance with thedetermined relative importance of performance versus power conservation,a current steering range for a stimulation channel defined by first andsecond physical electrodes communicatively coupled to the auditoryprosthesis. The current steering range is centered about a midpoint ofthe stimulation channel and may be determined in any suitable manner.

In step 706, the sound processor directs the auditory prosthesis toapply electrical stimulation representative of audio content having afrequency included in a frequency band associated with the stimulationchannel in accordance with the determined current steering range. Step706 may be performed in any of the ways described herein.

Various implementations and examples of the systems and methodsdescribed herein will now be provided. It will be recognized that theimplementations and examples provided herein are merely illustrative ofthe many different implementations and examples that may realized inaccordance with the systems and methods described herein.

In some implementations, a sound processor may set a current steeringrange associated with a particular stimulation channel in response toinput provided to the sound processor by a user. For example, a user maymanually switch between different stimulation programs by using a switchor the like included within or otherwise associated with the soundprocessor. Each stimulation program may specify a distinct currentsteering range that is to be associated with one or more stimulationchannels. Hence, in response to a user switching to a differentstimulation program, the sound processor may adjust one or more currentsteering ranges to one or more values specified by the differentstimulation program.

As mentioned, a sound processor may determine a relative importance ofperformance versus power conservation for an auditory prosthesis andthen determine, set, and/or adjust a current steering range associatedwith a stimulation channel in accordance with the determined relativeimportance. This may be performed in any suitable manner. For example,the sound processor may determine that an auditory prosthesis patient islocated within a particular environment (e.g., in a noisy restaurant),listening to a particular type of audio (e.g., music), and/or in anyother situation that requires a relatively high auditory prosthesisperformance level. At the same time, the sound processor may determinethat the need for conserving power is relatively low (e.g., bydetermining that an available amount of power within a battery supplyingpower to the auditory prosthesis is above a predetermined threshold). Inresponse, the sound processor may increase one or more current steeringranges associated with one or more stimulation channels in order toincrease a performance level of the auditory prosthesis.

Alternatively, the sound processor may determine that the auditoryprosthesis patient is located within a particular environment (e.g., ina quiet room), listening to a particular type of audio (e.g., speech),and/or in any other situation that does not require a relatively highauditory prosthesis performance level. At the same time, the soundprocessor may determine that the need for conserving power is relativelyhigh (e.g., by determining that an available amount of power within abattery supplying power to the auditory prosthesis is below apredetermined threshold). In response, the sound processor may decreaseone or more current steering ranges associated with one or morestimulation channels in order to reduce a compliance voltage that theauditory prosthesis has to maintain and thereby reduce power consumptionby the auditory prosthesis.

In some implementations, a sound processor may prevent any of thephysical electrodes connected to an auditory prosthesis from beingmapped to a particular frequency. In this manner, full current steeringmay not be used in any of the stimulation channels defined by thephysical electrodes. This ensures that current will always be splitamong at least two physical electrodes when representing a frequencyassociated with an audio signal.

To illustrate, FIG. 8 shows an exemplary mapping strategy 800 in which alimited current steering range is associated with each stimulationchannel formed by physical electrodes E1 through E4. As shown, physicalelectrodes E1 and E2 define a first stimulation channel 802-1, physicalelectrodes E2 and E3 define a second stimulation channel 802-2, andphysical electrodes E3 and E4 define a third stimulation channel 802-3.Each stimulation channel 802 has a particular frequency band 804 (e.g.,frequency bands 804-1 through 804-3) associated therewith. For example,frequency band 804-1 is associated with stimulation channel 802-1,frequency band 804-2 is associated with stimulation channel 802-2, andfrequency band 804-3 is associated with stimulation channel 802-3. FIG.8 also shows a frequency-to-electrode mapping 806 (e.g., mapping 806-1through 806-3) for each stimulation channel 802. As shown by mappings806, none of physical electrodes E1 through E4 have a frequency mappedthereto. Rather, each frequency between 300 Hz and 600 Hz is mapped tovirtual electrodes disposed in between the physical electrodes, therebyensuring that current will always be split between two physicalelectrodes.

In some examples, a sound processor may be configured to detect a needto minimize interaction between adjacent stimulation channels. As usedherein, “interaction between adjacent stimulation channels” (or simply“channel interaction”) refers to a situation wherein electricalstimulation applied via one stimulation channel at least partially masksthe electrical stimulation applied via another stimulation channel.Channel interaction may inhibit the ability of a patient to perceivefine structure information (e.g., information that facilitates theperception of pitch, spatial location, etc. of an audio signal) appliedvia either one of the stimulation channels. The detection of a need tominimize channel interaction may be performed in response to user input(e.g., user input indicating a request to decrease channel interaction)and/or automatically as may serve a particular implementation. Inresponse, the sound processor may decrease the current steering rangesassociated with each stimulation channel, thereby increasing a bufferbetween each current steering range and decreasing interaction betweenthe two stimulation channels.

In the preceding description, various exemplary embodiments have beendescribed with reference to the accompanying drawings. It will, however,be evident that various modifications and changes may be made thereto,and additional embodiments may be implemented, without departing fromthe scope of the invention as set forth in the claims that follow. Forexample, certain features of one embodiment described herein may becombined with or substituted for features of another embodimentdescribed herein. The description and drawings are accordingly to beregarded in an illustrative rather than a restrictive sense.

What is claimed is:
 1. A system comprising: a current steeringmanagement facility configured to set a current steering range for astimulation channel defined by first and second physical electrodescommunicatively coupled to an auditory prosthesis to be less than anentire physical range of the stimulation channel, the current steeringrange being centered about a midpoint of the stimulation channel; amapping facility communicatively coupled to the current steeringmanagement facility and configured to map each frequency included in afrequency band associated with the stimulation channel to one or morevirtual electrodes included in the current steering range of thestimulation channel; and a spectral analysis facility communicativelycoupled to the mapping facility and configured to detect a frequencyassociated with an audio signal and included within the frequency band;wherein the current steering management facility is further configuredto identify, within the one or more virtual electrodes, a virtualelectrode to which the detected frequency is mapped, and direct theauditory prosthesis to apply electrical stimulation representative ofthe detected frequency to a stimulation site associated with theidentified virtual electrode by concurrently stimulating the firstphysical electrode with a first current level and the second physicalelectrode with a second current level; and wherein a ratio of the firstcurrent level to the second current level is based on a position of theidentified virtual electrode within the current steering range of thestimulation channel.
 2. The system of claim 1, wherein the currentsteering management facility is configured to set the current steeringrange in response to input provided to the sound processor by a user. 3.The system of claim 1, wherein the current steering management facilityis further configured to: determine a relative importance of performanceversus power conservation for the auditory prosthesis; and automaticallyset the current steering range in accordance with the determinedrelative importance.
 4. The system of claim 1, wherein the currentsteering management facility is further configured to: detect a decreasein power available to the auditory prosthesis; and decrease the currentsteering range in response to the decrease in the available power. 5.The system of claim 1, wherein the current steering management facilityis configured to set the current steering range by setting a currentsteering range value to be equal to a value greater than or equal tozero and less than one, wherein a current steering range value of zerorepresents no current steering about the midpoint of the stimulationchannel, and wherein a current steering range value of one representsfull current steering about the midpoint of the stimulation channel. 6.The system of claim 1, wherein the first and second physical electrodesare not mapped to any of the frequencies included in the frequency band.7. The system of claim 1, wherein the current steering managementfacility is further configured to: detect a need to minimize interactionbetween the stimulation channel and an additional stimulation channeldefined by the second physical electrode and a third physical electrode;and decrease the current steering range in response to the detectedneed.
 8. The system of claim 1, wherein the current steering managementfacility is further configured to set a current steering range of one ormore additional stimulation channels associated with the auditoryprosthesis to be substantially equal to the current steering range ofthe stimulation channel.
 9. The system of claim 1, wherein the currentsteering management facility is further configured to set anothercurrent steering range for another stimulation channel associated withthe auditory prosthesis, the another current steering range beingdifferent than the current steering range of the stimulation channel.10. The system of claim 1, wherein the detected frequency comprises aminimum frequency included in the frequency band or a maximum frequencyincluded in the frequency band.
 11. A system comprising: an auditoryprosthesis; and a sound processor communicatively coupled to theauditory prosthesis and configured to determine a relative importance ofperformance versus power conservation for an auditory prosthesis,determine, in accordance with the determined relative importance ofperformance versus power conservation, a current steering range for astimulation channel defined by first and second physical electrodescommunicatively coupled to the auditory prosthesis, the current steeringrange centered about a midpoint of the stimulation channel, and directthe auditory prosthesis to apply electrical stimulation representativeof audio content having a frequency included in a frequency bandassociated with the stimulation channel in accordance with thedetermined current steering range.
 12. The system of claim 11, whereinthe sound processor is further configured to: detect a change in therelative importance of performance versus power conservation for theauditory prosthesis; dynamically adjust, in accordance with the detectedchange in the relative importance of performance versus powerconservation, the current steering range for the stimulation channel;and direct the auditory prosthesis to apply electrical stimulationrepresentative of additional audio content having a frequency includedin a frequency band associated with the stimulation channel inaccordance with the dynamically adjusted current steering range.
 13. Thesystem of claim 12, wherein the sound processor is configured to: detectthe change in the relative importance of performance versus powerconservation for the auditory prosthesis by detecting an increase in therelative importance of performance versus power conservation for theauditory prosthesis; and dynamically adjust the current steering rangefor the stimulation channel by increasing the current steering range.14. The system of claim 12, wherein the sound processor is configuredto: detect the change in the relative importance of performance versuspower conservation for the auditory prosthesis by detecting an decreasein the relative importance of performance versus power conservation forthe auditory prosthesis; and dynamically adjust the current steeringrange for the stimulation channel by decreasing the current steeringrange.
 15. A method comprising: setting, by a sound processor, a currentsteering range for a stimulation channel defined by first and secondphysical electrodes communicatively coupled to an auditory prosthesis tobe less than an entire physical range of the stimulation channel, thecurrent steering range being centered about a midpoint of thestimulation channel; mapping, by the sound processor, the frequenciesincluded in a frequency band associated with the stimulation channel toone or more virtual electrodes included in the current steering range ofthe stimulation channel; detecting, by the sound processor, a frequencyassociated with an audio signal and included within the frequency band;identifying within the one or more virtual electrodes, by the soundprocessor, a virtual electrode to which the detected frequency ismapped; and directing, by the sound processor, the auditory prosthesisto apply electrical stimulation representative of the detected frequencyto a stimulation site associated with the identified virtual electrodeby concurrently stimulating the first physical electrode with a firstcurrent level and the second physical electrode with a second currentlevel; wherein a ratio of the first current level to the second currentlevel is based on a position of the identified virtual electrode withinthe current steering range of the stimulation channel.
 16. The method ofclaim 15, wherein the setting of the current steering range is performedin response to input provided to the sound processor by a user.
 17. Themethod of claim 15, further comprising: determining, by a soundprocessor, a relative importance of performance versus powerconservation for the auditory prosthesis; wherein the setting of thecurrent steering range is performed automatically in accordance with thedetermined relative importance.
 18. The method of claim 15, furthercomprising: detecting, by the sound processor, a decrease in poweravailable to the auditory prosthesis; and decreasing, by the soundprocessor, the current steering range in response to the decrease in theavailable power.
 19. The method of claim 15, wherein: the setting of thecurrent steering range is performed by setting a current steering rangevalue to be equal to a value greater than or equal to zero and less thanone; a current steering range value of zero represents no currentsteering about the midpoint of the stimulation channel; and a currentsteering range value of one represents full current steering about themidpoint of the stimulation channel.
 20. A method comprising:determining, by a sound processor, a relative importance of performanceversus power conservation for an auditory prosthesis; determining, bythe sound processor in accordance with the determined relativeimportance of performance versus power conservation, a current steeringrange for a stimulation channel defined by first and second physicalelectrodes communicatively coupled to the auditory prosthesis, thecurrent steering range centered about a midpoint of the stimulationchannel; and directing, by the sound processor, the auditory prosthesisto apply electrical stimulation representative of audio content having afrequency included in a frequency band associated with the stimulationchannel in accordance with the determined current steering range.